Respirators are commonly worn by people working in areas where the air may be contaminated with toxic or noxious substances such as airborne particulates, gases, and vapors. For example, the air in a sanding or grinding area may contain airborne dust particles, the air in a painting area may contain solvent vapors or droplets of paint, and the air in a welding area may contain fumes that would be harmful to inhale. People working in these areas will often wear a respirator that either filters contaminated air before it reaches the breathing zone of the wearer or supplies the user with uncontaminated air from a remote air source.
The type of respirator used in a particular environment depends on the amount and type of protection required by the wearer. When it is desirable to protect both the eyes and respiratory system of a wearer, a device commonly referred to as a "loose fitting face piece" is often used. The term "loose fitting face piece" defines a classification of the American National Standards Institute (ANSI) for a respiratory protective system in which a face shield or some type of enclosure about the face is designed to form a partial seal with the face. Loose fitting face pieces typically do not cover the neck and shoulders of the wearer and may include a helmet or other headpiece to protect the head from flying or falling objects. In many cases, a face shield is designed to rotate with respect to the headgear between a position covering the face and eyes and a position away from the face.
In order to help prevent contaminated air from reaching the face and eyes of the wearer, loose fitting face pieces are often provided with a face seal. When the respirator is sealed in this way, the air pressure inside the mask can be either negative or positive as compared to the surrounding environment. A negative pressure respirator is designed to have a lower pressure inside the mask than the surrounding ambient air and requires an air-tight seal between the mask and the face of the wearer to prevent contaminated air from being pulled into the respirator. A positive pressure respirator is designed to have a higher pressure inside the mask than the surrounding air and commonly has at least one small opening to allow excess air that is under pressure in the mask to escape into the surrounding ambient air.
There are several known face seal designs used with loose fitting face pieces. One common face seal design includes a piece of fabric having one edge attached to the sides and lower portion of a rigid face shield piece and having elastic material along the other edge. When a user pulls the rigid face shield piece down to a position covering the face, the elastic edge typically contacts the front of the user's chin and mouth area. For user comfort and in order to assist in forming a proper seal, the user must reach up under the face shield piece to pull the elastic edge of the fabric underneath the chin. This process may be difficult and inconvenient for the user, particularly if that person needs to use both hands for some other task, or if the person is wearing cumbersome work gloves.
This face seal design can also be inconvenient for users who wear glasses under the face shield, because the elastic edge of the fabric can interfere with the corner of the glasses when the face shield is being pulled down over the face. This contact between the elastic and glasses can dislocate the glasses or cause the glasses to fall from the user's face.
Another face seal design involves the use of a U-shaped flange made of rubber or other resilient material positioned on the inside of the face shield to contact the cheeks and chin of the wearer and provide a seal. For example, U.S. Pat. No. 4,280,491 (Berg et al.), which is commonly owned by the assignee of the present invention, describes a respirator having U-shaped sealing means formed of a resilient material, such as foam, fastened along the peripheral edge of a frame to seal the face shield assembly along the sides and across the chin of the user's face. While these face seals can provide an adequate seal for some users, the seals may not be easily adaptable to accommodate different face and head sizes. Thus, these face seals may not be interchangeable between users.